Answer:
The correct answer will be option-B.
Explanation:
A scientific experimental must be designed in a way that it could be able to test the predicted hypothesis.
An experiment must divide the samples into two groups: the experimental design in which the independent variable will influence the dependent variable and the control group in which the variable to be tested is skipped and the independent variable does not influence the dependent variable.
Control group provides a reference to the experimental group, therefore, is considered important.
In the given question, since the scientist has concluded the results on the basis of his experimental groups only as it lacked a control group which could be used as reference therefore, leads to biased results on the basis of the experimental group.
Thus, Option-B is the correct answer.